When you're submitting anything; manuscript, short story, poems...anything, there is a waiting period. Some agents get back to you in under twenty minutes. Some competitions say "Winners announced in November". Some places that say "Winners announced X-Month" will get pushed back to "Z-Month". All I know is that it's a huge waiting game of hope, and fear, and anxiety, and nervousness when opening my e-mail. All the time I'm scared. But it's the good kind. I think.
Outside of that, if you get a request for a manuscript, you'll wait to hear back (most agents that I've read up on say -full- manuscript can take 4-8 weeks, sometimes longer). If you land an agent, you'll wait while they pitch for you. If you land a publisher, you'll wait for for your book to be published. (I know an author who waited 18 months for her novel to get published.)
Otherwise, if your submissions consist of literary magazines or contests you'll wait to hear back for the winner. Sometimes they move in advancements for rounds (in example: "Advance to round two" "Advance to round 50"). Even if you get accepted or win, chances are you'll be waiting for the publication.
So, if you're a writer and trying to get published, find things to do while you wait. I vote, write more. I hear it's the best way to fend off writer's block.